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  • richardmitnick 11:50 am on January 27, 2020 Permalink | Reply
    Tags: "This NASA Visualisation of a Black Hole Is So Beautiful We Could Cry", , , , , , Messier 87, ,   

    From NASA via Science Alert: “This NASA Visualisation of a Black Hole Is So Beautiful, We Could Cry” 

    From NASA

    via

    ScienceAlert

    Science Alert

    26 JAN 2020
    MICHELLE STARR

    1
    NASA Visualization Shows a Black Hole’s Warped World

    The first-ever direct image of a black hole’s event horizon was a truly impressive feat of scientific ingenuity. But it was extremely difficult to achieve, and the resulting image was relatively low-resolution.

    Mesier 87*, The first image of a black hole. First-ever direct image of a black hole, Messier 87*. (EHT Collaboration).This is the supermassive black hole at the center of the galaxy Messier 87. Image via JPL/ Event Horizon Telescope Collaboration.

    EHT map

    Now iconic image of Katie Bouman-Harvard Smithsonian Astrophysical Observatory after the image of Messier 87 was achieved. Headed from Harvard to Caltech as an Assistant Professor. On the committee for the next iteration of the EHT .

    Techniques and technology will be refined, and it’s expected that future direct images of black holes will improve with time. In September 2019, a NASA visualisation – made for the agency’s Black Hole Week – showed what we might expect to see in high-resolution images of an actively accreting supermassive black hole.

    Supermassive black holes sit at the centres of most large galaxies, and how they got there is a mystery; which came first, the black hole or the galaxy, is one of the big questions in cosmology.

    What we do know is that they are really huge, as in millions or billions of times the mass of the Sun; that they can control star formation; that when they wake up and start feeding, they can become the brightest objects in the Universe. Over the decades, we have also figured out some of their strange dynamics.

    In fact, the very first simulated image of a black hole, calculated using a 1960s punch card IBM 7040 computer and plotted by hand by French astrophysicist Jean-Pierre Luminet in 1978, still looks a lot like NASA’s simulation.

    In both simulations (the one above, and Luminet’s work below), you see a black circle in the centre. That’s the event horizon, the point at which electromagnetic radiation – light, radio waves, X-rays and so forth – are no longer fast enough to achieve escape velocity from the black hole’s gravitational pull.

    4
    (Jean-Pierre Luminet)

    Across the middle of the black hole is the front of the disc of material that is swirling around the black hole, like water into a drain. It generates such intense radiation through friction that we can detect this part with our telescopes – that’s what you are seeing in the picture of Messier 87*.

    You can see the photon ring, a perfect ring of light around the event horizon. And you can see a broad sweep of light around the black hole. That light is actually coming from the part of the accretion disc behind the black hole; but the gravity is so intense, even outside the event horizon, that it warps spacetime and bends the path of light around the black hole.

    You can also see that one side of the accretion disc is brighter than the other. This effect is called relativistic beaming, and it’s caused by the rotation of the disc. The part of the disc that is moving towards us is brighter because it is moving close to light-speed. This motion produces a change in frequency in the wavelength of the light. It’s called the Doppler effect.

    The side that’s moving away from us, therefore, is dimmer, because that motion has the opposite effect.

    “It is precisely this strong asymmetry of apparent luminosity,” Luminet wrote in a paper last year, “that is the main signature of a black hole, the only celestial object able to give the internal regions of an accretion disk a speed of rotation close to the speed of light and to induce a very strong Doppler effect.”

    Simulations such as these can help us understand the extreme physics around supermassive black holes – and that helps us understand what we are seeing when we look at the picture of Messier 87*.

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    The National Aeronautics and Space Administration (NASA) is the agency of the United States government that is responsible for the nation’s civilian space program and for aeronautics and aerospace research.

    President Dwight D. Eisenhower established the National Aeronautics and Space Administration (NASA) in 1958 with a distinctly civilian (rather than military) orientation encouraging peaceful applications in space science. The National Aeronautics and Space Act was passed on July 29, 1958, disestablishing NASA’s predecessor, the National Advisory Committee for Aeronautics (NACA). The new agency became operational on October 1, 1958.

    Since that time, most U.S. space exploration efforts have been led by NASA, including the Apollo moon-landing missions, the Skylab space station, and later the Space Shuttle. Currently, NASA is supporting the International Space Station and is overseeing the development of the Orion Multi-Purpose Crew Vehicle and Commercial Crew vehicles. The agency is also responsible for the Launch Services Program (LSP) which provides oversight of launch operations and countdown management for unmanned NASA launches. Most recently, NASA announced a new Space Launch System that it said would take the agency’s astronauts farther into space than ever before and lay the cornerstone for future human space exploration efforts by the U.S.

    NASA science is focused on better understanding Earth through the Earth Observing System, advancing heliophysics through the efforts of the Science Mission Directorate’s Heliophysics Research Program, exploring bodies throughout the Solar System with advanced robotic missions such as New Horizons, and researching astrophysics topics, such as the Big Bang, through the Great Observatories [Hubble, Chandra, Spitzer, and associated programs. NASA shares data with various national and international organizations such as from the [JAXA]Greenhouse Gases Observing Satellite.

     
  • richardmitnick 6:50 am on January 21, 2020 Permalink | Reply
    Tags: "The dynamic behaviour of a black hole corona", "XMM-Newton maps black hole surroundings", , , , Black hole IRAS 13224–3809, , , , Messier 87   

    From European Space Agency – United space in Europe (2): “The dynamic behaviour of a black hole corona” and “XMM-Newton maps black hole surroundings” 

    ESA Space For Europe Banner

    From European Space Agency – United space in Europe

    1. The dynamic behaviour of a black hole corona

    20/01/2020

    United space in Europe

    1
    XMM-Newton maps black hole surroundings. ESA

    The dynamic behaviour of a black hole corona

    These illustrations show the surroundings of a black hole feeding on ambient gas as mapped using ESA’s XMM-Newton X-ray observatory.

    ESA/XMM Newton

    As the material falls into the black hole, it spirals around to form a flattened disc, as shown here, heating up as it does so. At the very centre of the disc, close to the black hole, a region of very hot electrons – with temperatures of around a billion degrees – known as the corona produced high-energy X-rays that stream out into space.

    A new study has used the reverberating echoes of this radiation, as observed by XMM-Newton, to map the surroundings of a black hole. The study focussed on the black hole at the core of an active galaxy named IRAS 13224–3809, which is one of the most variable X-ray sources in the sky, undergoing very large and rapid fluctuations in brightness of a factor of 50 in mere hours.

    By tracking the X-ray echoes, it was possible to track the dynamic behaviour of the corona itself, where the intense X-ray emission originates from. The corona is shown here as the bright region hovering over the black hole, changing in size and brightness. The study found that the corona of the black hole within IRAS 13224–3809 changed in size incredibly quickly, over a matter of days.

    The Full Story

    2. XMM-Newton maps black hole surroundings

    20/01/2020

    William Alston
    Institute of Astronomy
    University of Cambridge, UK
    Email: wna@ast.cam.ac.uk

    Michael Parker
    European Space Agency
    European Space Astronomy Centre
    Villanueva de la Cañada, Madrid, Spain
    Email: Michael.Parker@esa.int

    Norbert Schartel
    XMM-Newton project scientist
    European Space Agency
    Email: norbert.schartel@esa.int

    Material falling into a black hole casts X-rays out into space – and now, for the first time, ESA’s XMM-Newton X-ray observatory [above] has used the reverberating echoes of this radiation to map the dynamic behaviour and surroundings of a black hole itself.

    Most black holes are too small on the sky for us to resolve their immediate environment, but we can still explore these mysterious objects by watching how matter behaves as it nears, and falls into, them.

    As material spirals towards a black hole, it is heated up and emits X-rays that, in turn, echo and reverberate as they interact with nearby gas. These regions of space are highly distorted and warped due to the extreme nature and crushingly strong gravity of the black hole.

    For the first time, researchers have used XMM-Newton to track these light echoes and map the surroundings of the black hole at the core of an active galaxy. Named IRAS 13224–3809, the black hole’s host galaxy is one of the most variable X-ray sources in the sky, undergoing very large and rapid fluctuations in brightness of a factor of 50 in mere hours.

    “Everyone is familiar with how the echo of their voice sounds different when speaking in a classroom compared to a cathedral – this is simply due to the geometry and materials of the rooms, which causes sound to behave and bounce around differently,” explains William Alston of the University of Cambridge, UK, lead author of the new study.

    “In a similar manner, we can watch how echoes of X-ray radiation propagate in the vicinity of a black hole in order to map out the geometry of a region and the state of a clump of matter before it disappears into the singularity. It’s a bit like cosmic echo-location.”

    As the dynamics of infalling gas are strongly linked to the properties of the consuming black hole, William and colleagues were also able to determine the mass and spin of the galaxy’s central black hole by observing the properties of matter as it spiralled inwards.

    The inspiralling material forms a disc as it falls into the black hole. Above this disc lies a region of very hot electrons – with temperatures of around a billion degrees – called the corona. While the scientists expected to see the reverberation echoes they used to map the region’s geometry, they also spotted something unexpected: the corona itself changed in size incredibly quickly, over a matter of days.

    “As the corona’s size changes, so does the light echo – a bit like if the cathedral ceiling is moving up and down, changing how the echo of your voice sounds,” adds William.

    “By tracking the light echoes, we were able to track this changing corona, and – what’s even more exciting – get much better values for the black hole’s mass and spin than we could have determined if the corona was not changing in size. We know the black hole’s mass cannot be fluctuating, so any changes in the echo must be down to the gaseous environment.”

    The study used the longest observation of an accreting black hole ever taken with XMM-Newton, collected over 16 spacecraft orbits in 2011 and 2016 and totalling 2 million seconds – just over 23 days.

    This, combined with the strong and short-term variability of the black hole itself, allowed William and collaborators to model the echoes comprehensively over day-long timescales.

    The region explored in this study is not accessible to observatories such as the Event Horizon Telescope [EHT], which managed to take the first ever picture of gas in the immediate vicinity of a black hole – the one sitting at the centre of the nearby massive galaxy Messier 87.

    EHT map

    The result, based on observations performed with radio telescopes across the world in 2017 and published last year, immediately became a global sensation.

    M87*, The first image of a black hole. This is the supermassive black hole at the center of the galaxy Messier 87. Image via JPL/ Event Horizon Telescope Collaboration.

    Now iconic image of Katie Bouman-Harvard Smithsonian Astrophysical Observatory after the image of Messier 87 was achieved. Headed from Harvard to Caltech as an Assistant Professional. On the committee for the next iteration of the EHT .

    “The Event Horizon Telescope image was obtained using a method known as interferometry – a wonderful technique that can only work on the very few nearest supermassive black holes to Earth, such as those in Messier 87 and in our home galaxy, the Milky Way, because their apparent size on the sky is large enough for this method to work,” says co-author Michael Parker, who is an ESA research fellow at the European Space Astronomy Centre near Madrid, Spain.

    “By contrast, our approach is able to probe the nearest few hundred supermassive black holes that are actively consuming matter – and this number will increase significantly with the launch of ESA’s Athena satellite.”

    ESA/Athena spacecraft depiction

    Characterising the environments closely surrounding black holes is a core science goal for ESA’s Athena mission, which is scheduled for launch in the early 2030s and will unveil the secrets of the hot and energetic Universe.

    Measuring the mass, spin and accretion rates of a large sample of black holes is key to understanding gravity throughout the cosmos.

    Additionally, since supermassive black holes are strongly linked to their host galaxy’s properties, these studies are also key to furthering our knowledge of how galaxies form and evolve over time.

    “The large dataset provided by XMM-Newton was essential for this result,” says Norbert Schartel, ESA XMM-Newton Project Scientist.

    “Reverberation mapping is an exciting technique that promises to reveal much about both black holes and the wider Universe in coming years. I hope that XMM-Newton will perform similar observing campaigns for several more active galaxies in coming years, so that the method is fully established when Athena launches.”

    Science paper:
    A dynamic black hole corona in an active galaxy through X-ray reverberation mapping by W. N. Alston et al.
    Nature Astronomy.

    The study uses data gathered by XMM-Newton’s European Photon Imaging Camera (EPIC).

    See the “dynamic behaviour”full article here .

    See the “Full Story” article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    The European Space Agency (ESA), established in 1975, is an intergovernmental organization dedicated to the exploration of space, currently with 19 member states. Headquartered in Paris, ESA has a staff of more than 2,000. ESA’s space flight program includes human spaceflight, mainly through the participation in the International Space Station program, the launch and operations of unmanned exploration missions to other planets and the Moon, Earth observation, science, telecommunication as well as maintaining a major spaceport, the Guiana Space Centre at Kourou, French Guiana, and designing launch vehicles. ESA science missions are based at ESTEC in Noordwijk, Netherlands, Earth Observation missions at ESRIN in Frascati, Italy, ESA Mission Control (ESOC) is in Darmstadt, Germany, the European Astronaut Centre (EAC) that trains astronauts for future missions is situated in Cologne, Germany, and the European Space Astronomy Centre is located in Villanueva de la Cañada, Spain.

    ESA50 Logo large

     
  • richardmitnick 8:16 pm on January 6, 2020 Permalink | Reply
    Tags: "Famous Black Hole Has Jet Pushing Cosmic Speed Limit", , , , , , Messier 87,   

    From NASA Chandra: “Famous Black Hole Has Jet Pushing Cosmic Speed Limit” 

    NASA Chandra Banner

    NASA/Chandra Telescope


    From NASA Chandra

    1
    Credit: NASA/CXC/SAO/B.Snios et al.

    1.6.20

    The Event Horizon Telescope Collaboration released the first image of a black hole with observations of the massive, dark object at the center of Messier 87 last April.

    The first image of a black hole. This is the supermassive black hole at the center of the galaxy Messier 87. Image via JPL/ Event Horizon Telescope Collaboration.

    Now iconic image of Katie Bouman-Harvard Smithsonian Astrophysical Observatory after the image of Messier 87 was achieved. Headed from Harvard to Caltech as an Assistant Professional. On the committee for the next iteration of the EHT .

    EHT map

    This black hole has a mass of about 6.5 billion times that of the sun and is located about 55 million light years from Earth. The black hole has been called M87* by astronomers and has recently been given the Hawaiian name of “Powehi.”

    For years, astronomers have observed radiation from a jet of high energy particles — powered by the black hole — blasting out of the center of Messier 87. They have studied the jet in radio, optical, and X-ray light, including with Chandra. And now by using Chandra observations, researchers have seen that sections of the jet are moving at nearly the speed of light.

    “This is the first time such extreme speeds by a black hole’s jet have been recorded using X-ray data,” said Ralph Kraft of the Center of Astrophysics | Harvard & Smithsonian (CfA) in Cambridge, Mass., who presented the study at the American Astronomical Society meeting in Honolulu, Hawaii. “We needed the sharp X-ray vision of Chandra to make these measurements.”

    When matter gets close enough to a black hole, it enters into a swirling pattern called an accretion disk. Some material from the inner part of the accretion disk falls onto the black hole and some of it is redirected away from the black hole in the form of narrow beams, or jets, of material along magnetic field lines. Because this infall process is irregular, the jets are made of clumps or knots that can sometimes be identified with Chandra and other telescopes.

    The researchers used Chandra observations from 2012 and 2017 to track the motion of two X-ray knots located within the jet about 900 and 2,500 light years away from the black hole. The X-ray data show motion with apparent speeds of 6.3 times the speed of light for the X-ray knot closer to the black hole and 2.4 times the speed of light for the other.

    “One of the unbreakable laws of physics is that nothing can move faster than the speed of light,” said co-author Brad Snios, also of the CfA. “We haven’t broken physics, but we have found an example of an amazing phenomenon called superluminal motion.”

    Superluminal motion occurs when objects are traveling close to the speed of light along a direction that is close to our line of sight. The jet travels almost as quickly towards us as the light it generates, giving the illusion that the jet’s motion is much more rapid than the speed of light. In the case of M87*, the jet is pointing close to our direction, resulting in these exotic apparent speeds.

    Astronomers have previously seen such motion in Messier 87*’s jet at radio and optical wavelengths, but they have not been able to definitively show that matter in the jet is moving at very close to the speed of light. For example, the moving features could be a wave or a shock, similar to a sonic boom from a supersonic plane, rather than tracing the motions of matter.

    This latest result shows the ability of X-rays to act as an accurate cosmic speed gun. The team observed that the feature moving with an apparent speed of 6.3 times the speed of light also faded by over 70% between 2012 and 2017. This fading was likely caused by particles’ loss of energy due to the radiation produced as they spiral around a magnetic field. For this to occur the team must be seeing X-rays from the same particles at both times, and not a moving wave.

    3
    Illustration of the Supermassive Black Hole at the Center of Messier 87 (Credit: NASA/CXC/M.Weiss)

    4
    Chandra Wide-field View of Messier 87; box shows the approximate location of the wide-field jet image above (Credit: NASA/CXC)


    A Quick Look at the Black Hole Jet in Messier 87

    “Our work gives the strongest evidence yet that particles in Messier 87*’s jet are actually traveling at close to the cosmic speed limit”, said Snios.

    The Chandra data are an excellent complement to the EHT data. The size of the ring around the black hole seen with the Event Horizon Telescope is about a hundred million times smaller than the size of the jet seen with Chandra.

    Another difference is that the EHT observed Messier 87 over six days in April 2017, giving a recent snapshot of the black hole. The Chandra observations investigate ejected material within the jet that was launched from the black hole hundreds and thousands of years earlier.

    “It’s like the Event Horizon Telescope is giving a close-up view of a rocket launcher,” said the CfA’s Paul Nulsen, another co-author of the study, “and Chandra is showing us the rockets in flight.”

    In addition to being presented at the AAS meeting, these results are also described in a paper in The Astrophysical Journal led by Brad Snios.
    Other materials about the findings are available at:
    http://chandra.si.edu

    For more Chandra images, multimedia and related materials, visit:
    http://www.nasa.gov/chandra

    Media contacts:
    Megan Watzke
    Chandra X-ray Center, Cambridge, Mass.
    617-496-7998
    mwatzke@cfa.harvard.edu

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    NASA’s Marshall Space Flight Center in Huntsville, Ala., manages the Chandra program for NASA’s Science Mission Directorate in Washington. The Smithsonian Astrophysical Observatory controls Chandra’s science and flight operations from Cambridge, Mass.

     
  • richardmitnick 2:21 pm on December 28, 2019 Permalink | Reply
    Tags: , , , , , , , Event Horizon, Messier 87,   

    From Ethan Siegel: “Ask Ethan: Can Black Holes Ever Spit Anything Back Out?” 

    From Ethan Siegel
    Dec 28, 2019

    A black hole’s event horizon is thought of as the point of no return. But perhaps there are ways back out, after all.

    Black holes just might be the most extreme objects that exist in the entire Universe. While every quantum of matter or energy is affected by the gravitational force, there are other forces capable of overcoming gravity everywhere you go, except inside a black hole. The most important feature of a black hole is the existence of an event horizon; no other class of object has them. Although black holes have this region where gravity is so strong that nothing can escape, not even if they move at the speed of light, perhaps there are loopholes to the inescapability of a black hole’s gravity, after all. That’s the subject of this week’s question, which comes from Noah, who asks,

    Do black holes ever spit things out at any time?

    And if they do, do they ever spit out light?

    The answer must be yes. After all, the most surprising thing about black holes — both predicted theoretically and observed directly — is that they aren’t black at all.

    1
    The second-largest black hole as seen from Earth, the one at the center of the galaxy Messier 87, is shown in three views here. At the top is optical from Hubble, at the lower-left is radio from NRAO, and at the lower-right is X-ray from Chandra. These differing views have different resolutions dependent on the optical sensitivity, wavelength of light used, and size of the telescope mirrors used to observe them. These are all examples of radiation emitted from the regions around black holes, demonstrating that black holes aren’t so black, after all. (TOP, OPTICAL, HUBBLE SPACE TELESCOPE / NASA / WIKISKY; LOWER LEFT, RADIO, NRAO / VERY LARGE ARRAY (VLA); LOWER RIGHT, X-RAY, NASA / CHANDRA X-RAY TELESCOPE)

    NASA/ESA Hubble Telescope

    NRAO/Karl V Jansky Expanded Very Large Array, on the Plains of San Agustin fifty miles west of Socorro, NM, USA, at an elevation of 6970 ft (2124 m)

    NASA/Chandra X-ray Telescope

    If black holes were entirely dark, there would be no way to detect them at all, save for the gravitational influence that they might have on the other objects around them. If we had a black hole and a star in orbit around one another, we’d be able to infer the existence (and the mass) of the black hole simply by watching how the star appeared to move over time.

    As it wobbled back-and-forth in its orbit, we could determine the parameters of the other object present, including the mass, orbital separation distance, and if our measurements were good enough, even its angle-of-inclination relative to our line of sight. Based on the light that comes from it, we could know whether it was a star, a white dwarf, a neutron star, or — if there were no light at all — even a black hole.

    2
    When a black hole and a companion star orbit one another, the star’s motion will change over time owing to the gravitational influence of the black hole, while matter from the star can accrete onto the black hole, resulting in X-ray and radio emissions. (JINGCHUAN YU/BEIJING PLANETARIUM/2019)

    But in our practical, realistic Universe, the black holes that orbit other stars are actually detectable through radiation.

    “Hang on,” you might object, “if black holes are regions of space from which nothing can escape, not even light, then how are we seeing radiation coming from the black hole itself?”

    That’s a valid point, but what you have to understand is that the space outside of a black hole’s event horizon doesn’t have to be devoid of matter. In fact, if there’s another star nearby, that star can serve as a rich source of matter, capable of being siphoned onto the black hole, particularly if the nearby star is giant and diffuse. This sort of system, in particular, creates what we observe as an X-ray binary, and it’s how the first black hole we ever found was detected.

    3
    Black holes are not isolated objects in space, but exist amidst the matter and energy in the Universe, galaxy, and star systems where they reside. They grow by accreting and devouring matter and energy, and when they actively feed they emit X-rays. Binary black hole systems that emit X-rays are how the majority of our known non-supermassive black holes were discovered. (NASA/ESA HUBBLE SPACE TELESCOPE COLLABORATION)

    Matter, if you break it down to a subatomic level, is made of charged particles. Put this matter in the vicinity of a black hole, and it will:

    move rapidly,
    collide with other matter particles,
    heat up,
    create electric currents and magnetic fields,
    accelerate,
    and emit radiation.

    Some of the matter will lose momentum and fall into the black hole, passing through the event horizon and adding to the black hole’s mass. However, the majority of the matter won’t fall in at all, but rather will get funneled into an accretion disk (or more generally, an accretion flow) that experiences the electromagnetic forces from all the accelerating matter. As a result, we see two jets that get expelled in opposite directions emanating from black holes.

    4
    While distant host galaxies for quasars and active galactic nuclei can often be imaged in visible/infrared light, the jets themselves and the surrounding emission is best viewed in both the X-ray and the radio, as illustrated here for the galaxy Hercules A. The gaseous outflows are highlighted in the radio, and if X-ray emissions follow the same path into the gas, they can be responsible for creating hot spots owing to the acceleration of electrons. (NASA, ESA, S. BAUM AND C. O’DEA (RIT), R. PERLEY AND W. COTTON (NRAO/AUI/NSF), AND THE HUBBLE HERITAGE TEAM (STSCI/AURA))

    These relativistic jets are made of particles aAn illustration of an active black hole, one that accretes matter and accelerates a portion of it outwards in two perpendicular jets. The normal matter undergoing an acceleration like this describes how quasars work extremely well, while the accretion flows are ultimately responsible for the emitted particles and radiation we observe. (MARK A. GARLICK)nd emit enormous amounts of light from their dynamical interactions with the particles in the interstellar medium. In fact, the same physics is at play in the supermassive black holes found at the centers of galaxies: matter that falls in towards the black hole largely gets ripped apart, funneled into accretion flows, accelerated, and ejected in jet-like structures.

    If you were a real particle outside of the black hole’s event horizon, but were gravitationally bound to the black hole, you’d be compelled to move in an elliptical orbit around it. At your point of closest approach — the periapsis of your orbit — you’ll be moving at your fastest speed, which gives you the greatest likelihood of interacting with other particles. If they’re present, you’ll experience inelastic collisions, friction, electromagnetic forces, etc. In other words, all the forces that cause charged particles to emit radiation.

    5
    An illustration of an active black hole, one that accretes matter and accelerates a portion of it outwards in two perpendicular jets. The normal matter undergoing an acceleration like this describes how quasars work extremely well, while the accretion flows are ultimately responsible for the emitted particles and radiation we observe. (MARK A. GARLICK)

    Radiation, although it covers the entire electromagnetic spectrum from low-energy radio waves all the way up to X-rays and gamma rays, is just the general term for all forms of light. So long as you have particles that exist outside of the black hole’s event horizon, they will create this form of radiation, and in the cases where relatively nearby black holes are feeding at fast enough rates, we’ll actually observe that characteristic X-ray radiation.

    In fact, we can even look at the supermassive black holes from outside our own galaxy, and find those same features, only scaled up in both power and extent. The same physics is at play — charged object in motion create magnetic fields, and those fields accelerate particles along one particular axis — which is what creates the relativistic jets we observe from a distance. Those jets produce showers of both particles and radiation, and we can catch them even from Earth, sometimes even in visible light.

    6
    The galaxy Centaurus A, shown in a composite of visible light, infrared (submillimeter) light and in the X-ray. This is the nearest active galaxy to the Milky Way, and its bipolar jets are thought to arise from the active, feeding black hole inside. (ESO/WFI (OPTICAL); MPIFR/ESO/APEX/A.WEISS ET AL. (SUBMILLIMETRE); NASA/CXC/CFA/R.KRAFT ET AL. (X-RAY))

    Wide Field Imager on the 2.2 meter MPG/ESO telescope at Cerro LaSilla

    ESO/MPIfR APEX high on the Chajnantor plateau in Chile’s Atacama region, at an altitude of over 4,800 m (15,700 ft)

    In some cases, where black holes are active and feeding, we can even observe a spectacular phenomenon known as a photon sphere. Around black holes, the fabric of space is so severely curved that it isn’t just particles that make circular-and-elliptical orbits around that central mass, but even photons: light itself.

    The photon sphere is a little bit larger than the event horizon, and for realistic (rotating) black holes, the physics is more complicated than a simple, non-rotating case. However, the extreme curvature of space means that these photons will create a ring-like structure visible from any faraway perspective. The ring itself is larger than the event horizon, and the curvature of space makes the angular size of the ring appear even larger than that, but this is one of the things we need to calculate in order to understand why our first image of a black hole’s event horizon appears with the famous donut-like shape we observe.

    The first image of a black hole. This is the supermassive black hole at the center of the galaxy Messier 87. Image via JPL/ Event Horizon Telescope Collaboration.

    Event Horizon Telescope Array

    Arizona Radio Observatory
    Arizona Radio Observatory/Submillimeter-wave Astronomy (ARO/SMT)

    ESO/APEX
    Atacama Pathfinder EXperiment

    CARMA Array no longer in service
    Combined Array for Research in Millimeter-wave Astronomy (CARMA)

    Atacama Submillimeter Telescope Experiment (ASTE)
    Atacama Submillimeter Telescope Experiment (ASTE)

    Caltech Submillimeter Observatory
    Caltech Submillimeter Observatory (CSO)

    IRAM 30m Radio telescope, on Pico Veleta in the Spanish Sierra Nevada,, Altitude 2,850 m (9,350 ft)


    Institut de Radioastronomie Millimetrique (IRAM) 30m

    James Clerk Maxwell Telescope interior, Mauna Kea, Hawaii, USA
    James Clerk Maxwell Telescope interior, Mauna Kea, Hawaii, USA

    Large Millimeter Telescope Alfonso Serrano
    Large Millimeter Telescope Alfonso Serrano

    CfA Submillimeter Array Mauna Kea, Hawaii, USA, Altitude 4,080 m (13,390 ft)

    Submillimeter Array Hawaii SAO

    ESO/NRAO/NAOJ ALMA Array
    ESO/NRAO/NAOJ ALMA Array, Chile

    South Pole Telescope SPTPOL
    South Pole Telescope SPTPOL

    Future Array/Telescopes

    IRAM NOEMA in the French Alps on the wide and isolated Plateau de Bure at an elevation of 2550 meters, the telescope currently consists of ten antennas, each 15 meters in diameter.interferometer, Located in the French Alpes on the wide and isolated Plateau de Bure at an elevation of 2550 meters

    NSF CfA Greenland telescope


    Greenland Telescope

    ARO 12m Radio Telescope, Kitt Peak National Observatory, Arizona, USA, Altitude 1,914 m (6,280 ft)


    ARO 12m Radio Telescope

    Caltech Owens Valley Radio Observatory, located near Big Pine, California (US) in Owens Valley, Altitude1,222 m (4,009 ft)

    All of that, however, as interesting and light-emitting as it may be, only arises from material that hasn’t yet fallen through that critical region of space around the black hole: it’s all for things that remain outside the event horizon. Nothing can be seen arising from any material that actually goes inside the event horizon and winds up physically over that critical boundary.

    However, if you could create a black hole that was completely isolated from everything else in the Universe — isolated from particles, radiation, neutrinos, dark matter, other sources of mass, etc. — all you’d have was the curved space resulting from the black hole’s presence itself. Unlike the static picture of curved space that you typically see, any particle at rest would feel as though the space it occupies is being dragged around and into the black hole; it’s as though the space beneath a particle’s proverbial “feet” is in motion, as though it’s fundamentally on a moving walkway.

    8
    In the vicinity of a black hole, space flows like either a moving walkway or a waterfall, depending on how you want to visualize it. At the event horizon, even if you ran (or swam) at the speed of light, there would be no overcoming the flow of spacetime, which drags you into the singularity at the center. Outside the event horizon, though, other forces (like electromagnetism) can frequently overcome the pull of gravity, causing even infalling matter to escape. (ANDREW HAMILTON / JILA / UNIVERSITY OF COLORADO)

    You’d have that curved space, an event horizon, and the laws of physics. And one of the things that the laws of physics teaches us is that the quantum fields that govern the Universe, even in the absence of any particles, are still present, constantly fluctuating as they inevitably must.

    In flat space, this wouldn’t be a big deal. Energy fluctuations occur in the quantum vacuum, and in flat space, the quantum vacuum has equivalent properties everywhere. But when you have curved space — and in particular, space that’s more severely curved in one direction (towards the black hole) than the other (away from the black hole) — observers at different locations will disagree as to what the correct description of the lowest-energy state of the vacuum is.

    9
    Visualization of a quantum field theory calculation showing virtual particles in the quantum vacuum. (Specifically, for the strong interactions.) Even in empty space, this vacuum energy is non-zero, and what appears to be the ‘ground state’ in one region of curved space will look different from the perspective of an observer where the spatial curvature differs. (DEREK LEINWEBER)

    For someone far away from the event horizon, where space appears flat, they’ll observe some low-energy radiation coming from the more severely curved regions of space, even in the absence of any particles. This radiation carries real energy, and is a consequence of how quantum fields behave in curved space. The greater the curvature of space, the greater the rate that this radiation — known as Hawking radiation — gets emitted.

    The energy for the radiation only has one possible source: it has to be stolen from the mass of the black hole. Fortunately, Einstein’s most famous equation, E = mc², describes this balance exactly. The smaller in mass the black hole is, the smaller the event horizon and the greater the curvature is near it. When you put this together, you wind up with a fascinating discovery: the less massive your black hole is, the more quickly it loses mass, emits Hawking radiation, and decays away.

    Cosmic microwave background radiation. Stephen Hawking Center for Theoretical Cosmology U Cambridge

    9
    The event horizon of a black hole is a spherical or spheroidal region from which nothing, not even light, can escape. But outside the event horizon, the black hole is predicted to emit radiation. Hawking’s 1974 work was the first to demonstrate this, and it was arguably his greatest scientific achievement. (NASA; DANA BERRY, SKYWORKS DIGITAL, INC.)

    The rate at which an isolated black hole radiates its mass away, through Hawking radiation, is incredibly slow for any realistic black hole in our Universe. A black hole of our Sun’s mass would take 10⁶⁷ years to evaporate, while the one at the Milky Way’s center needs 10⁸⁷ years and the most massive ones known take up to 10¹⁰⁰ years!

    Still, this is the only case where we can say that some form of energy from inside the black hole’s event horizon affects what we observe outside of it. The things that fall in through a black hole’s event horizon don’t come out again, not under any circumstances. The only things that a black hole can spit out come from outside the event horizon, from particles to conventional photons to even the Hawking radiation that get their energy from the black hole’s mass itself. There may be plenty of light that arises from black holes, but none of it can ever come from inside the event horizon.

    SGR A* , the supermassive black hole at the center of the Milky Way. NASA’s Chandra X-Ray Observatory

    SgrA* NASA/Chandra supermassive black hole at the center of the Milky Way, X-ray image of the center of our galaxy, where the supermassive black hole Sagittarius A* resides. Image via X-ray: NASA/UMass/D.Wang et al., IR: NASA/STScI.

    Star S0-2 Andrea Ghez Keck/UCLA Galactic Center Group at SGR A*, the supermassive black hole at the center of the milky way

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
  • richardmitnick 9:58 am on December 25, 2019 Permalink | Reply
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    From ALMA: “In the Shadow of a Black Hole” 

    ESO/NRAO/NAOJ ALMA Array in Chile in the Atacama at Chajnantor plateau, at 5,000 metres

    From ALMA

    10 April, 2019

    Nicolás Lira
    Education and Public Outreach Coordinator
    Joint ALMA Observatory, Santiago – Chile
    Phone: +56 2 2467 6519
    Cell phone: +56 9 9445 7726
    Email: nicolas.lira@alma.cl

    Masaaki Hiramatsu
    Education and Public Outreach Officer, NAOJ Chile
    Observatory
, Tokyo – Japan
    Phone: +81 422 34 3630
    Email: hiramatsu.masaaki@nao.ac.jp

    Bárbara Ferreira
    ESO Public Information Officer
    Garching bei München, Germany
    Phone: +49 89 3200 6670
    Email: pio@eso.org

    Iris Nijman
    Public Information Officer
    National Radio Astronomy Observatory Charlottesville, Virginia – USA
    Cell phone: +1 (434) 249 3423
    Email: alma-pr@nrao.edu

    The Event Horizon Telescope (EHT) — a planet-scale array of eight ground-based radio telescopes forged through international collaboration — was designed to capture images of a black hole. In coordinated press conferences across the globe, EHT researchers revealed that they succeeded, unveiling the first direct visual evidence of a supermassive black hole and its shadow.
    This 17-minute film explores the efforts that led to this historic image, from the science of Einstein and Schwarzschild to the struggles and successes of the EHT collaboration. Credit:ESO

    Event Horizon Telescope Array

    Arizona Radio Observatory
    Arizona Radio Observatory/Submillimeter-wave Astronomy (ARO/SMT)

    ESO/APEX
    Atacama Pathfinder EXperiment

    CARMA Array no longer in service
    Combined Array for Research in Millimeter-wave Astronomy (CARMA)

    Atacama Submillimeter Telescope Experiment (ASTE)
    Atacama Submillimeter Telescope Experiment (ASTE)

    Caltech Submillimeter Observatory
    Caltech Submillimeter Observatory (CSO)

    IRAM 30m Radio telescope, on Pico Veleta in the Spanish Sierra Nevada,, Altitude 2,850 m (9,350 ft)


    Institut de Radioastronomie Millimetrique (IRAM) 30m

    James Clerk Maxwell Telescope interior, Mauna Kea, Hawaii, USA
    James Clerk Maxwell Telescope interior, Mauna Kea, Hawaii, USA

    Large Millimeter Telescope Alfonso Serrano
    Large Millimeter Telescope Alfonso Serrano

    CfA Submillimeter Array Mauna Kea, Hawaii, USA, Altitude 4,080 m (13,390 ft)

    Submillimeter Array Hawaii SAO

    ESO/NRAO/NAOJ ALMA Array
    ESO/NRAO/NAOJ ALMA Array, Chile

    South Pole Telescope SPTPOL
    South Pole Telescope SPTPOL

    Future Array/Telescopes

    IRAM NOEMA in the French Alps on the wide and isolated Plateau de Bure at an elevation of 2550 meters, the telescope currently consists of ten antennas, each 15 meters in diameter.interferometer, Located in the French Alpes on the wide and isolated Plateau de Bure at an elevation of 2550 meters

    NSF CfA Greenland telescope


    Greenland Telescope

    ARO 12m Radio Telescope, Kitt Peak National Observatory, Arizona, USA, Altitude 1,914 m (6,280 ft)


    ARO 12m Radio Telescope

    Caltech Owens Valley Radio Observatory, located near Big Pine, California (US) in Owens Valley, Altitude1,222 m (4,009 ft)

    The first image of a black hole. This is the supermassive black hole at the center of the galaxy Messier 87. Image via JPL/ Event Horizon Telescope Collaboration.

    Katie Bouman-Harvard Smithsonian Astrophysical Observatory. Headed to Caltech.

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership of Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA is funded in Europe by the European Organization for Astronomical Research in the Southern Hemisphere (ESO), in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and in East Asia by the National Institutes of Natural Sciences (NINS) of Japan in cooperation with the Academia Sinica (AS) in Taiwan.

    ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI) and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA.

    NRAO Small
    ESO 50 Large

     
  • richardmitnick 3:57 pm on December 3, 2019 Permalink | Reply
    Tags: , , , , , , Messier 87, ,   

    From Sky&Telescope: “The Appearance of a Black Hole’s Shadow” 

    SKY&Telescope bloc

    From Sky & Telescope

    In April of this year, the Event Horizon Telescope captured the first detailed images of the shadow of a black hole. In a new study, a team of scientists has now explored what determines the size and shape of black hole shadows like this one.

    2
    Simulation of accreting gas swirling around a supermassive black hole. How do the details of this gas affect the observed appearance of the black hole’s shadow?
    Jordy Davelaar et al. / Radboud University / BlackHoleCam

    Messier 87 supermassive black hole from the EHT

    The stunning new radio images of the supermassive black hole in nearby galaxy Messier 87, released this spring by the Event Horizon Telescope team, revealed a bright ring of emission surrounding a dark, circular region.

    This distinct structure is a result of the warped spacetime around massive objects like black holes. The ring of light is comprised of photons from the hot, radiating gas that surrounds the black hole, whose paths have been bent around the black hole before arriving at our telescopes. The dark region in the center is termed the black hole’s “shadow”; this is the collection of paths of photons that did not escape, but were instead captured by the black hole.

    3
    Comparison of conceptions of a black hole surrounded by a thin accretion disk vs. a thick accretion disk.
    Top: NASA ; bottom: Nicolle R. Fuller / NSF

    The Shape of Accretion

    While some previous studies have explored what a black hole shadow looks like when the black hole is surrounded by a very thin disk of accreting gas (think the black hole + disk from the movie Interstellar), most supermassive black holes — like Messier 87, or our own supermassive black hole, Sagittarius A* — are more likely to be surrounded by hot, accreting gas that is more broadly distributed, forming a thick or quasi-spherical disk.

    ,SgrA* NASA/Chandra supermassive black hole at the center of the Milky Way, X-ray image of the center of our galaxy, where the supermassive black hole Sagittarius A* resides. Image via X-ray: NASA/UMass/D.Wang et al., IR: NASA/STScI.

    SGR A* , the supermassive black hole at the center of the Milky Way. NASA’s Chandra X-Ray Observatory

    Does the geometry and motion of the accreting gas affect the size and shape of a black hole’s shadow?

    Models of Monsters

    In a new study, three scientists — Ramesh Narayan and Michael Johnson (Harvard-Smithsonian Center for Astrophysics) and Charles Gammie (University of Illinois at Urbana–Champaign) — have teamed up to explore how a black hole’s shadow changes based on the behavior of the hot gas around it.

    4
    The image of the black hole shadow for three of the authors’ models: non-relativistic spacetime (top), relativistic spacetime with static surrounding gas (center), and relativistic spacetime with accreting gas flowing radially inwards (bottom).
    Adapted from Narayan et al. 2019

    Narayan, Johnson, and Gammie built analytical models of a black hole surrounded by hot, optically thin gas (which means that the radiation escapes the gas and is observable). They then analyzed how the shadow would appear using different spacetimes, with different gas motions, and with different behaviors of the gas close to the black hole.

    Reducing Complications

    Intriguingly, the authors found that the appearance of the black hole’s shadow doesn’t depend on the details of the gas accretion close to the black hole. The size of the shadow was primarily determined by the spacetime itself (which is impacted by the mass of the black hole). But how the gas is distributed around the black hole, and whether that gas is stationary or accreting, doesn’t hugely affect the appearance of the shadow.

    Real life is a little messier than this simple, spherically symmetric model; black hole spin and the presence of jets or outflows will cause asymmetries in the shadow. But the authors’ results generally tell us that the close-in details of accretion flows aren’t complicating what we’re seeing. And that’s valuable information we can use as we interpret future observations of black hole shadows!

    Science paper
    The Astrophysical Letters
    https://iopscience.iop.org/article/10.3847/2041-8213/ab518c

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    Sky & Telescope magazine, founded in 1941 by Charles A. Federer Jr. and Helen Spence Federer, has the largest, most experienced staff of any astronomy magazine in the world. Its editors are virtually all amateur or professional astronomers, and every one has built a telescope, written a book, done original research, developed a new product, or otherwise distinguished him or herself.

    Sky & Telescope magazine, now in its eighth decade, came about because of some happy accidents. Its earliest known ancestor was a four-page bulletin called The Amateur Astronomer, which was begun in 1929 by the Amateur Astronomers Association in New York City. Then, in 1935, the American Museum of Natural History opened its Hayden Planetarium and began to issue a monthly bulletin that became a full-size magazine called The Sky within a year. Under the editorship of Hans Christian Adamson, The Sky featured large illustrations and articles from astronomers all over the globe. It immediately absorbed The Amateur Astronomer.

    Despite initial success, by 1939 the planetarium found itself unable to continue financial support of The Sky. Charles A. Federer, who would become the dominant force behind Sky & Telescope, was then working as a lecturer at the planetarium. He was asked to take over publishing The Sky. Federer agreed and started an independent publishing corporation in New York.

    “Our first issue came out in January 1940,” he noted. “We dropped from 32 to 24 pages, used cheaper quality paper…but editorially we further defined the departments and tried to squeeze as much information as possible between the covers.” Federer was The Sky’s editor, and his wife, Helen, served as managing editor. In that January 1940 issue, they stated their goal: “We shall try to make the magazine meet the needs of amateur astronomy, so that amateur astronomers will come to regard it as essential to their pursuit, and professionals to consider it a worthwhile medium in which to bring their work before the public.”

     
  • richardmitnick 1:14 pm on November 19, 2019 Permalink | Reply
    Tags: , , , , , Messier 87,   

    From École Polytechnique Fédérale de Lausanne: Women in STEM- “Katie Bouman, the scientist who reveals the invisible” 


    From École Polytechnique Fédérale de Lausanne

    11.18.19
    Sarah Perrin

    Katie Bouman-Harvard Smithsonian Astrophysical Observatory. Now at Caltech.

    1

    The first-ever image of a black hole was unveiled to the public this past April.

    Messier 87 supermassive black hole from the EHT

    It was produced by a team of 200 scientists as part of the Event Horizon Telescope Project. Katie Bouman, an assistant professor at Caltech, was at the center of the action. On a recent visit to EPFL, she talked about computer science with President Martin Vetterli.

    Katie Bouman was one of 200 scientists who helped create the first-ever image of a black hole, released this past April. The 30-year old researcher, who was recently named an assistant professor of computing and mathematical sciences at the California Institute of Technology (CalTech), came to speak at EPFL’s Open Science Day. Martin Vetterli took advantage of that opportunity to sit down with her and ask her a few questions about their field of shared interest.

    MV: “It’s pretty unusual for someone to become a star researcher at such a young age. How did you get into science?

    KB: I was very interested in science as a kid. When I was in third grade, I remember looking under rocks all the time. And as I got older, I was constantly drawn to the different science topics covered in class. In sixth grade, I first got involved in science fair projects, and I continued doing that on and off through high school. Then, when I tried out research for the first time, I was thrilled: it was so different from a homework set, where you know there’s a solution even if it’s difficult to find. Research was a new way of thinking and problem-solving for me, and I found that very exciting.

    How did you get into computer science?

    It wasn’t until high school, when a friend convinced me to take a computer science class. At first, I thought: “This isn’t very fun, what will I use it for?” But it opened up a totally new area for me! We didn’t solve any big problems or anything, but because I had done this class and learned this new computing language, I was offered a position the following summer to work in a lab at Purdue University, in my hometown, helping the graduate researchers with their projects. Some were working on imaging problems, such as in the field of forensics. It was so exciting to see how we could pull information out of images and use it to recover hidden properties about the world. From that point on, I got more and more interested in imaging and electrical engineering and eventually computer vision. My path has always been guided by a love of research and images, because I really like the fact that you can visualize what you’re working on.

    The black-hole imaging project was very cross-disciplinary. What was it like to work on this team?

    It was quite a new experience, and I had a lot of fun! At that point, the team had already worked extensively on the instrumentation side and was just getting started on the imaging part. They really needed someone who could interpret the data and develop new ways of dealing with the challenges. I first heard about the project through a presentation and, actually, I understood pretty much nothing, it was like gibberish [laughter]. Still, I left that presentation thinking “I want to be part of this!”, because I could see that the tools needed for this project were so similar to the ones we were developing for other problems, like in medical imaging. When I joined the team, I didn’t know anything about black holes. But I was working with an amazing group of researchers. They kindly taught me everything I needed to know about radioastronomy, astrophysics, black holes, and so on. I also got to spend about a month and a half behind a telescope learning about the technical system. And I think that process was important, because when you’re developing an imaging method, you have to understand not only how problems arise during observations and make their way into the data you’re analyzing, but also what you can expect to find. In order to get the most out of the data, you need to learn as much as possible in the related fields. That’s why working in cross-disciplinary teams is so crucial now for many big science projects to go forward.

    Helping create the first image of a black hole is a major accomplishment so early in your career. What’s next for you as a young researcher at CalTech?

    I’m really excited to do new things. For example, I’m starting to work on seismology – trying to image earthquakes – which is crucial for the California region. I’m very excited about this job because CalTech is a small school, which makes it easier to connect with people in other fields. I’m so fortunate to already be working with a lot of people in different areas. My ultimate goal is to think about how we can help scientists discover new things. We are so used to coming up with our own hypotheses and figuring out what we should observe to test them. But we can now develop machines to find trends and data that we might not see or be aware of as humans. I’m really interested in how to design machines that can tell us how to do our experiments, and what new wavelength or data domain to look at in order to discover something we would not otherwise see. In general, I’m very much into how we do data-driven scientific discovery.

    A couple of guys just won the Nobel Prize for discovering the first exoplanet 25 years ago. Initially, they didn’t believe their results and reran the experiment several times. Some things have changed since then, but we’re still dealing with noisy data, right?

    Yes, when we first created the black-hole image, or at least the day we got the data, we entered it into an imaging script and a ring appeared. I actually went from being really excited to being mad at the colleagues who gave us the data – which I was convinced were fake. It just seemed too good to be true! Nothing ever works like that the first time. It was just so much more beautiful than any synthetic data we had created. It actually took weeks before I believed the data were real, and that our colleagues weren’t trying to trick us or test us.

    See the full article here
    .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    EPFL bloc

    EPFL campus

    EPFL is Europe’s most cosmopolitan technical university. It receives students, professors and staff from over 120 nationalities. With both a Swiss and international calling, it is therefore guided by a constant wish to open up; its missions of teaching, research and partnership impact various circles: universities and engineering schools, developing and emerging countries, secondary schools and gymnasiums, industry and economy, political circles and the general public.

     
  • richardmitnick 8:38 am on May 4, 2019 Permalink | Reply
    Tags: , , , , , Messier 87,   

    From JPL-Caltech: “The Giant Galaxy Around the Giant Black Hole” 

    NASA JPL Banner

    From JPL-Caltech

    1

    The galaxy Messier 87, imaged here by NASA’s Spitzer Space Telescope, is home to a supermassive black hole that spews two jets of material out into space at nearly the speed of light. The inset shows a close-up view of the shockwaves created by the two jets.Credit: NASA/JPL-Caltech/IPAC

    NASA/Spitzer Infrared Telescope

    On April 10, 2019, the Event Horizon Telescope (EHT) unveiled the first-ever image of a black hole’s event horizon, the area beyond which light cannot escape the immense gravity of the black hole.

    The first image of a black hole, Messier 87 Credit Event Horizon Telescope Collaboration, via NSF and ERC 4.10.19

    That giant black hole, with a mass of 6.5 billion Suns, is located in the elliptical galaxy Messier 87. EHT is an international collaboration whose support in the U.S. includes the National Science Foundation.

    This image from NASA’s Spitzer Space Telescope shows the entire M87 galaxy in infrared light. The EHT image, by contrast, relied on light in radio wavelengths and showed the black hole’s shadow against the backdrop of high-energy material around it.

    EHT map

    Located about 55 million light-years from Earth, Messier 87 has been a subject of astronomical study for more than 100 years and has been imaged by many NASA observatories, including the Hubble Space Telescope, the Chandra X-ray Observatory and NuSTAR.

    NASA/ESA Hubble Telescope

    NASA/Chandra X-ray Telescope

    NASA/DTU/ASI NuSTAR X-ray telescope

    In 1918, astronomer Heber Curtis first noticed “a curious straight ray” extending from the galaxy’s center. This bright jet of high-energy material, produced by a disk of material spinning rapidly around the black hole, is visible in multiple wavelengths of light, from radio waves through X-rays. When the particles in the jet impact the interstellar medium (the sparse material filling the space between stars in M87), they create a shockwave that radiates in infrared and radio wavelengths of light but not visible light. In the Spitzer image, the shockwave is more prominent than the jet itself.

    The brighter jet, located to the right of the galaxy’s center, is traveling almost directly toward Earth. Its brightness is amplified due to its high speed in our direction, but even more so because of what scientists call “relativistic effects,” which arise because the material in the jet is traveling near the speed of light. The jet’s trajectory is just slightly offset from our line of sight with respect to the galaxy, so we can still see some of the length of the jet. The shockwave begins around the point where the jet appears to curve down, highlighting the regions where the fast-moving particles are colliding with gas in the galaxy and slowing down.

    The second jet, by contrast, is moving so rapidly away from us that the relativistic effects render it invisible at all wavelengths. But the shockwave it creates in the interstellar medium can still be seen here.

    Located on the left side of the galaxy’s center, the shockwave looks like an inverted letter “C.” While not visible in optical images, the lobe can also be seen in radio waves, as in this image from the National Radio Astronomy Observatory’s Very Large Array.

    Close-up from VLA of a jet near black hole in Messier 87

    NRAO/Karl V Jansky Expanded Very Large Array, on the Plains of San Agustin fifty miles west of Socorro, NM, USA, at an elevation of 6970 ft (2124 m)

    By combining observations in the infrared, radio waves, visible light, X-rays and extremely energetic gamma rays, scientists can study the physics of these powerful jets. Scientists are still striving for a solid theoretical understanding of how gas being pulled into black holes creates outflowing jets.

    Infrared light at wavelengths of 3.6 and 4.5 microns are rendered in blue and green, showing the distribution of stars, while dust features that glow brightly at 8.0 microns are shown in red. The image was taken during Spitzer’s initial “cold” mission.

    The Jet Propulsion Laboratory in Pasadena, California, manages the Spitzer Space Telescope mission for NASA’s Science Mission Directorate in Washington. Science operations are conducted at the Spitzer Science Center at Caltech in Pasadena. Space operations are based at Lockheed Martin Space Systems in Littleton, Colorado. Data are archived at the Infrared Science Archive housed at IPAC at Caltech.

    More information on Spitzer can be found at its website: http://www.spitzer.caltech.edu/

    See the full article here .


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    Please help promote STEM in your local schools.

    Stem Education Coalition

    NASA JPL Campus

    Jet Propulsion Laboratory (JPL)) is a federally funded research and development center and NASA field center located in the San Gabriel Valley area of Los Angeles County, California, United States. Although the facility has a Pasadena postal address, it is actually headquartered in the city of La Cañada Flintridge, on the northwest border of Pasadena. JPL is managed by the nearby California Institute of Technology (Caltech) for the National Aeronautics and Space Administration. The Laboratory’s primary function is the construction and operation of robotic planetary spacecraft, though it also conducts Earth-orbit and astronomy missions. It is also responsible for operating NASA’s Deep Space Network.

    Caltech Logo

    NASA image

     
  • richardmitnick 10:51 am on April 28, 2019 Permalink | Reply
    Tags: , , , , Messier 87, NGC 4258, , ,   

    From Science News: “The M87 black hole image showed the best way to measure black hole masses” 

    From Science News

    April 22, 2019
    Lisa Grossman

    Its diameter suggests the black hole is 6.5 billion times the mass of the sun.

    1
    SUPERMASSIVE SOURCE The gases and stars in galaxy Messier 87, shown in this composite image from the Chandra X-ray telescope and the Very Large Array, gave different numbers for the mass of the galaxy’s supermassive black hole.

    NASA/Chandra X-ray Telescope

    NRAO/Karl V Jansky Expanded Very Large Array, on the Plains of San Agustin fifty miles west of Socorro, NM, USA, at an elevation of 6970 ft (2124 m)

    The measure of a black hole is what it does with its stars.

    That’s one lesson astronomers are taking from the first-ever picture of a black hole, released on April 10 by an international telescope team (SN Online: 4/10/19).

    2
    SHADOW SIZE The Event Horizon Telescope captured the first image of M87’s black hole. That image showed that the black hole’s mass is about 6.5 billion times the mass of the sun, close to what astronomers expected based on the galaxy’s stars.

    That image confirmed that the mass of the supermassive black hole in the center of galaxy Messier 87 is close to what astronomers expected from how nearby stars orbit — solving a long-standing debate over how best to measure a black hole’s mass.

    The black hole in Messier 87, which is located about 55 million light-years from Earth, is the first black hole whose mass has been calculated by three precise methods: measuring the motion of stars, the swirl of surrounding gases and now, thanks to the Event Horizon Telescope imaging project, the diameter of the black hole’s shadow.

    EHT map

    In 1978, the first mass estimates to track the motions of stars whipping around the great gravitational center found that the stars must be orbiting something containing about 5 billion times the mass of the sun. A more precise estimate in 2011 using a similar stellar technique bumped its heft up to 6.6 billion times the mass of the sun.

    Star S0-2 Andrea Ghez Keck/UCLA Galactic Center Group at SGR A*, the supermassive black hole at the center of the milky way

    Meanwhile, astronomers in 1994 made another estimate by tracing how gases closer to the black hole than the stars swirl around the behemoth. That technique suggested that the black hole was 2.4 billion solar masses, which was revised in 2013 to 3.5 billion solar masses.

    For years, it wasn’t clear which technique got closer to the truth.

    Now the EHT picture showing a glowing orange ring of gases and dust around the black hole has solved the conflict. According to Einstein’s general theory of relativity, the diameter of the dark space in the center of the image — the black hole’s shadow — is directly related to its mass.

    “Bigger black holes cast bigger shadows,” EHT team member Michael Johnson, an astrophysicist at the Harvard Smithsonian Center for Astrophysics, said April 12 at a talk at MIT. “Easy check, we can see whether one or the other of these [mass measuring methods] is correct.” The shadow of M87’s black hole yielded a diameter of 38 billion kilometers, which let astronomers calculate a mass of 6.5 billion suns [The Astrophysical Journal Letters]— very close to the mass suggested by the motion of stars.

    The size of the shadow also negated the idea that the black hole is a wormhole, a theoretical bridge between distant points in spacetime (SN: 5/31/14, p. 16). If M87’s black hole had been a wormhole, theory predicts it should look smaller than it does. “It’s a stunning confirmation” of general relativity, Johnson said. “We instantly rule out all these exotic possibilities.”

    The mass confirmation may boost confidence in current simulations for how black holes develop, says Priyamvada Natarajan, a Yale University astrophysicist who was not involved with the EHT project. Most black hole mass estimates already use the stellar technique, in part because it’s easier to track a galaxy’s stars from farther away.

    3
    STARS AND STREAKS Astrophysicists have used both stars and gases to weigh in on the mass of the black hole in the galaxy NGC 4258, shown in this composite image. P.Ogle et al/Caltech/CXC/NASA, R.Gendler, STScI/NASA, Caltech-JPL/NASA, VLA/NRAO/NSF

    SGR A* , the supermassive black hole at the center of the Milky Way. NASA’s Chandra X-Ray Observatory

    Two other black holes whose masses have been measured in multiple ways, the Milky Way’s Sagittarius A* [Astronomy and Astrophysics] and the galaxy NGC 4258’s black hole, also suggest the star method works better. “These three cases now offer renewed faith in our current method,” Natarajan says.

    That faith won’t solve the most pressing black hole problems, such as how black holes grew so big so fast in the early universe — at least not right away (SN Online: 3/16/18). The gas versus star measurement of the M87 black hole mass differed by only a factor of two, which is not enough to explain how it got so massive in the first place. A black hole could double its mass in about a million years, at most.

    “What we don’t know is how we get supermassive black holes within a billion years,” says Hannalore Gerling-Dunsmore, a former Caltech physicist who is joining the University of Colorado Boulder later this year. She was not on the EHT team. “Once you’re already that big, what’s a million years between friends?”

    See the full article here .


    NSF press conference on the EHT Messier 87 Black Hole project


    European Research Council press conference on the EHT Messier 87 Black Hole project


    Katie Bouman on the EHT Messier 87 Black Hole project at Caltech


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  • richardmitnick 2:24 pm on April 27, 2019 Permalink | Reply
    Tags: "Ask Ethan: How Can A Black Hole’s Singularity Spin?", , , , Messier 87   

    From Ethan Siegel: “Ask Ethan: How Can A Black Hole’s Singularity Spin?” 

    From Ethan Siegel
    Apr 27, 2019

    If a star spins and then collapses, what happens to its angular momentum?

    1
    An accretion disk, magnetic fields and jets of material are all outside the black hole’s event horizon. Our classical picture of a steady disk, however, only applies to a non-rotating black hole. If you get close to the event horizon itself, rotating, realistic black holes offer some fascinating novel physics for us to consider. (M. WEISS/CFA)

    The most common way to form a black hole in the Universe is to have a massive star reach the end of its life and explode in a catastrophic supernova. However, while the outside portions of the star are blown apart, the inner core collapses, forming a black hole if the progenitor star is massive enough. But most real stars, including our Sun, are spinning. Therefore — since angular momentum is always conserved — they shouldn’t be able to collapse down to a single point. How does this all work? That’s what our Patreon supporter Aaron Weiss wants to know, asking:

    How [is] angular momentum conserved when stars collapse to black holes? What [does] it means for a black hole to spin? What is actually spinning? How can a singularity spin? Is there a “speed limit” to this spin rate and how does the spin affect the size of the event horizon and the area immediately around it?

    These are all good questions. Let’s find out.

    2
    The gravitational behavior of the Earth around the Sun is not due to an invisible gravitational pull, but is better described by the Earth falling freely through curved space dominated by the Sun. The shortest distance between two points isn’t a straight line, but rather a geodesic: a curved line that’s defined by the gravitational deformation of spacetime. (LIGO/T. PYLE)

    3
    In a Universe that isn’t expanding, you can fill it with stationary matter in any configuration you like, but it will always collapse down to a black hole. Such a Universe is unstable in the context of Einstein’s gravity, and must be expanding to be stable, or we must accept its inevitable fate. (E. SIEGEL / BEYOND THE GALAXY)

    Once you get matter with a sufficient amount of mass confined to a small enough volume, an event horizon will form at a particular location. A spherical region of space, whose radius is defined by the quantity of mass inside of it, will experience such severe curvature that anything passing interior to its boundary will be unable to escape.

    Outside of this event horizon, it will appear as though there is just an extreme region where gravity is very intense, but no light or matter can be emitted from within it. To anything that falls inside, however, it inevitably gets brought towards the very center of this black hole: towards a singularity. While the laws of physics break down at this point — some physicists cheekily refer to singularities as places where “God divided by zero” — no one doubts that all the matter and radiation that passes inside the event horizon heads towards this point-like region of space.

    3
    An illustration of heavily curved spacetime, outside the event horizon of a black hole. As you get closer and closer to the mass’s location, space becomes more severely curved, eventually leading to a location from within which even light cannot escape: the event horizon. The radius of that location is set by the mass of the black hole, the speed of light, and the laws of General Relativity alone. In theory, there should be a special point, a singularity, where all the mass is concentrated for stationary, spherically-symmetric black holes. (PIXABAY USER JOHNSONMARTIN)

    I can hear the objections already. After all, there are a legitimate number of ways the actual Universe works differently from this naive picture of gravitational collapse.

    The gravitational force isn’t the only one in the Universe: nuclear forces and electromagnetism play a role when it comes to matter and energy, too.
    Black holes aren’t formed from the collapse of a uniform distribution of matter, but rather by the implosion of a massive star’s core when nuclear fusion can no longer continue.
    And, perhaps most importantly, all stars we’ve ever discovered spin, and angular momentum is always conserved, so black holes should be spinning, too.

    So let’s do it: let’s go from the realm of a simplistic approximation to a more realistic picture of how black holes truly work.

    4
    In 2006, Mercury transited across the Sun, but the large sunspot visible on the Sun’s disk actually reduced its light output by a greater factor. By observing the locations of sunspots moving over time, we have determined that the Sun exhibits differential rotation, with the equator and poles taking anywhere from 25 to 33 Earth days to make a complete revolution. (WILLIAMS COLLEGE; GLENN SCHNEIDER, JAY PASACHOFF, AND SURANJIT TILAKAWARDANE)

    All stars spin. Our Sun, a relatively slow rotator, completes a full 360° turn on timescales ranging from 25 to 33 days, depending on which particular solar latitude you’re monitoring. But our Sun is huge and very low-density, and there are far more extreme objects in the Universe in terms of small physical sizes and large masses. Just as a spinning figure skater speeds up when they bring their arms and legs in, astrophysical masses rotate more quickly if you decrease their radius.

    If the Sun were a white dwarf — with the same mass but the physical size of Earth — it would rotate once every 4 minutes.

    If it became a neutron star — with the same mass but a radius of 20 km — it would rotate once every 2.4 milliseconds: consistent with what we observe for the fastest pulsars.

    5
    A neutron star is one of the densest collections of matter in the Universe, but there is an upper limit to their mass. Exceed it, and the neutron star will further collapse to form a black hole. The fastest-spinning neutron star we’ve ever discovered is a pulsar that revolves 766 times per second: faster than our Sun would spin if we collapsed it down to the size of a neutron star. (ESO/LUÍS CALÇADA)

    Well, if our star (or any star) collapsed down to a black hole, we’d still have to conserve angular momentum. When something spins in this Universe, there’s no way to just get rid of it, the same way you can’t create or destroy energy or momentum. It has to go somewhere. When any collection of matter collapses down to a radius smaller than the radius of an event horizon, that angular momentum is trapped inside there, too.

    This is okay! Einstein put forth his theory of General Relativity in 1915, and it was only a few months later that Karl Schwarzschild found the first exact solution: for a point mass, the same as a spherical black hole. The next step in modeling this problem in a more realistic fashion — to consider what if the black hole also has angular momentum, instead of mass alone — wasn’t solved until Roy Kerr found the exact solution in 1963.

    6
    The exact solution for a black hole with both mass and angular momentum was found by Roy Kerr in 1963. It revealed, instead of a single event horizon with a point-like singularity, an inner and outer event horizon, as well as an inner and outer ergosphere, plus a ring-like singularity of substantial radius. (MATT VISSER, ARXIV:0706.0622)

    There are some fundamental and important differences between the more naive, simpler Schwarzschild solution and the more realistic, complex Kerr solution. In no particular order, here are some fascinating contrasts:

    1.Instead of a single solution for where the event horizon is, a rotating black hole has two mathematical solutions: an inner and and outer event horizon.
    2.Outside of even the outer event horizon, there is a place known as the ergosphere, where space itself is dragged around at a rotational speed equal to the speed of light, and particles falling in there experience enormous accelerations.
    3.There is a maximum ratio of angular momentum to mass that is allowed; if there is too much angular momentum, the black hole will radiate that energy away (via gravitational radiation) until it’s below that limit.
    4.And, perhaps most fascinatingly, the singularity at the black hole’s center is no longer a point, but rather a 1-dimensional ring, where the radius of the ring is determined by the mass and angular momentum of the black hole.

    7
    The visible/near-IR photos from Hubble show a massive star, about 25 times the mass of the Sun, that has winked out of existence, with no supernova or other explanation. Direct collapse is the only reasonable candidate explanation, and is one known way, in addition to supernovae or neutron star mergers, to form a black hole. (NASA/ESA/C. KOCHANEK (OSU))

    All of this is true for a rotating black hole from the instant you create the event horizon for the first time. A high-mass star can go supernova, where the spinning core implodes and collapses down to a black hole, and all of this will be true. In fact, there is even some hope that if a supernova goes off in our own local group, LIGO might be able to detect the gravitational waves from a rapidly rotating black hole’s ring down.

    If you form a black hole from a neutron star-neutron star merger or the direct collapse of a star or gas cloud, the same possibilities hold true. But once your black hole exists, its angular momentum can constantly change as new matter or material falls in. The size of the event horizon can grow, and the size of the singularity and ergosphere can grow or shrink depending on the angular momentum of the new material that gets added.

    4
    Due to the properties of the rotating, dragged space near a realistic black hole with angular momentum, individual particles that would form planar orbits around non-rotating masses wind up occupying a large, torus-like shape in three dimensions. (MAARTEN VAN DE MEENT / WIKIMEDIA COMMONS)

    This leads to some fascinating behavior that you might not expect. In the case of a non-rotating black hole, a particle of matter outside of it can orbit, escape, or fall inside, but will remain in the same plane. When a black hole rotates, however, it gets dragged around through all three dimensions, where it will fill a torus-like region surrounding the black hole’s equator.

    There’s also an important distinction between a mathematical solution and a physical solution. If I told you I had the (square root of 4) oranges, you would conclude that I had 2 oranges. You could have just as easily concluded, mathematically, that I had -2 oranges, because the square root of 4 could just as easily be -2 as it could be +2. But in physics, there’s only one meaningful solution. As scientists have long noted, though:

    ” …you should not physically trust in the inner horizon or the inner ergosurface. Although they are certainly there as mathematical solutions of the exact vacuum Einstein equations, there are good physics reasons to suspect that the region at and inside the inner horizon, which can be shown to be a Cauchy horizon, is grossly unstable — even classically — and unlikely to form in any real astrophysical collapse.”

    7
    Shadow (black) & horizons and ergospheres (white) of a rotating black hole. The quantity of a, shown varying in the image, has to do with the relationship of angular momentum of the black hole to its mass. Note that the shadow as seen by the Event Horizon Telescope of the black hole is much larger than either the event horizon or ergosphere of the black hole itself. (YUKTEREZ (SIMON TYRAN, VIENNA) / WIKIMEDIA COMMONS)

    Now that we’ve finally observed a black hole’s event horizon for the first time, owing to the incredible success of the Event Horizon Telescope [EHT], scientists have been able to compare their observations with theoretical predictions. By running a variety of simulations detailing what the signals of black holes with various masses, spins, orientations, and accreting matter flows would be, they’ve been able to come up with the best fit for what they saw. Although there are some substantial uncertainties, the black hole at the center of M87 appears to be:

    rotating at 94% of its maximum speed,
    with a 1-dimensional ring singularity with a diameter of ~118 AU (larger than Pluto’s orbit),
    with its rotational axis pointing away from Earth at ~17°,
    and that all of the observations are consistent with a Kerr (which is favored over a Schwarzschild) black hole.

    The first image of a black hole, Messier 87 Credit Event Horizon Telescope Collaboration, via NSF 4.10.19

    In April of 2017, all 8 of the telescopes/telescope arrays associated with the Event Horizon Telescope pointed at Messier 87. This is what a supermassive black hole looks like, where the event horizon is clearly visible.

    EHT map

    Only through VLBI could we achieve the resolution necessary to construct an image like this, but the potential exists to someday improve it by a factor of hundreds. The shadow is consistent with a rotating (Kerr) black hole. (EVENT HORIZON TELESCOPE COLLABORATION ET AL.)

    Perhaps the most profound takeaway from all of this, though, is that in a rotating spacetime, space itself can indeed move without any sort of speed limit at all. It’s only the motion of matter and energy through space that’s limited by the speed of light; space itself has no such speed limit. In the case of a rotating black hole, there is a region of space beyond the event horizon where space is dragged around the black hole at a speed faster than the speed of light, and this is just fine. Matter still cannot move through that space at speeds exceeding the ultimate cosmic speed limit, and all of this is consistent with both relativity and what we observe.

    As more black holes are imaged and more and improved observations come in, we fully expect to learn even more about the physics of real, spinning black holes. But until then, know that our theory and observation are guiding us in a direction that’s tremendously profound, self-consistent, and — above all — the best approximation of reality that we currently have.

    See the full article here .

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    Please help promote STEM in your local schools.

    Stem Education Coalition

    “Starts With A Bang! is a blog/video blog about cosmology, physics, astronomy, and anything else I find interesting enough to write about. I am a firm believer that the highest good in life is learning, and the greatest evil is willful ignorance. The goal of everything on this site is to help inform you about our world, how we came to be here, and to understand how it all works. As I write these pages for you, I hope to not only explain to you what we know, think, and believe, but how we know it, and why we draw the conclusions we do. It is my hope that you find this interesting, informative, and accessible,” says Ethan

     
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